Another view of the Plan 9 mailing list 9fans. On first glance, it appears easier to read than the web interface https://marc.info/?l=9fans which I used before.

TAP, the Test Anything Protocol, is a simple text-based interface between testing modules in a test harness. It decouples the reporting of errors from the presentation of the reports.
Found on https://www.cliki.net/Test%20Framework